Disc drives are used for data storage in modern electronic products ranging from digital cameras to computer systems and networks. Typically, a disc drive includes a mechanical portion, or head disc assembly (HDA), and electronics in the form of a printed circuit board assembly (PCB), mounted to an outer surface of the HDA. The PCB controls HDA functions and provides an interface between the disc drive and its host.
Generally, a HDA comprises one or more magnetic discs affixed to a spindle motor assembly for rotation at a constant speed, an actuator assembly supporting an array of read/write heads that traverse generally concentric data tracks radially spaced across the disc surfaces and a voice coil motor (VCM) providing rotational motion to the actuator assembly. Continued demand for disc drives with ever increasing levels of data storage capacity, faster data throughput and decreasing price per megabyte have led disc drive manufacturers to seek ways to increase the storage capacity and improve overall operating efficiencies of the disc drive. Present generation disc drives typically achieve aerial bit densities of several gigabits per square centimeter, Gbits/cm2. Increasing recording densities can be achieved by increasing the number of bits stored along each track or bits per inch (BPI), generally requiring improvements in the read/write channel electronics, and/or by increasing the number of tracks per unit width or tracks per inch (TPI), generally requiring improvements in servo control systems.
One approach taken by disc drive manufacturers to increase recording density is through reduction in fly height of the read/write heads. Reducing the fly height of the read/write heads decreases the surface area occupied by data, thereby increasing number of bits capable of being stored on the on the surface area of the rotatable disc surface, which promotes an increase in both BPI and TPI.
Typically, disc drive manufacturers select a region on each rotatable disc surface, referred to as a landing zone, for the read/write head to land on and take off from. In most applications, the landing zone has a non-smooth or textured surface to mitigate a phenomenon referred to as stiction, an adhesion of the read/write head to the rotatable disc surface as a result of two smooth surfaces coming in contact with each other. One method of providing this non-smooth surface is to texturize the landing zone using a laser beam. The laser beam is held at an energy output level sufficient cause a plurality of minute eruptions on the otherwise smooth rotatable disc surface. The result of the process is a laser zone texture (LZT).
Subsequent to the texturing process, one of the final steps in a media preparation process is the application of a carbon overcoat. The carbon overcoat serves as a wear surface between the read/write head and a magnetic recording layer of the disc. Breakdown of a carbon overcoat leads to corrosion of the magnetic recording layer, which eventually renders the entire rotatable disc surface inoperable, as a magnetic storage medium.
The height of the plurality of laser eruptions is typically controlled to be no greater than a nominal fly height of read/write head. Therefore as fly heights of the read/write heads decrease, the height of the laser eruptions of the landing zone likewise decreases. The decrease in height of the laser eruptions results in an increase in surface area exposure of the rotatable disc surface to the read/write head. As the non-smooth textured surface approaches a smooth surface, adhesion between the read/write head and the landing zone of the rotatable disc surface increases. An increase in adhesion between the read/write head and the landing zone results in extending contact time between the read/write head and the disc surface during spin up of the disc drive. Extending the contact time accelerates wear of the carbon overcoat, which reduces the operating life of the disc drive.
Therefore, challenges remain and a need persists for techniques that reduce contact time between the read/write head and the rotatable disc surface during take off and extend the operating life of the carbon overcoat protecting the magnetic layer of the rotatable disc surface.